The elasticity of tissues varies and changes with age and is also influenced by various other parameters, such as health, fatigue, influence of exterior factors and the like. It is one of the main aims of therapeutic cosmetics to increase the elasticity and humidity of the skin, and thus to restore its youthful appearance and to prevent formation of wrinkles. According to the present invention an objective method of measurement is provided, which makes possible to evaluation of the elasticity of human skin in vivo before and after application of certain cosmetic preparations, thus providing both an objective test for the efficacy of such preparations and for their effect on the individual treated with same.
According to the present invention a sensitive instrument is presented which makes possible accurate measurements, providing data which are valuable in accurate evaluations of measurements of compressibility, humidity, viscosity and elasticity, and thus of the effects of various cosmetic preparations.
The novel instrument comprises mechanical and/or magneto-electronic means for the measurement of certain parameters indicative of the elasticity of tissues, and especially of human skin, in vivo, and especially in the lower part of the stress-strain curve of such tissues.
According to a further feature of the present invention means are provided for evaluation of the stretchability of human skin by applying a small predetermined pull on the skin in vivo. According to a preferred embodiment the contact of the probe with the skin is maintained by the application of vacuum-suction. The results thus obtained are indicative of the condition of the skin and also related to the quantity and nature of wrinkles.
The probe is applied to the tissue which is being tested, and vacuum is applied via a conduit in the probe and certain values thus measured are also indicative of parameters connected with the elasticity of the tissue. Further features of this novel and specific embodiment will be illustrated hereinafter.
The device according to the present invention is a modification of the instrument described by H. Schade, Z. fuer exp.Pathol. u. Therapie, 11, (1912) 369-399 and permits accurate measurement in a range of values substantially lower than the standard one used by Schade for his measurements, namely about 100 g/cm.sup.2. Furthermore, according to a preferred embodiment of the present invention means are provided for also carrying out measurements involving the application of suction (by applying a vacuum via the probe).
The probe of the novel instrument comprises a measuring area of the order of about 3 to 8 mm diameter, and preferably of about 5 mm diameter, which is about 0.2 cm.sup.2 area. The surface of the probe is advantageously an inert plastic material, such as Teflon or the like, and according to the preferred embodiment providing for the application of suction, it is provided with a throughgoing conduit, and in this case the surface of the probe advantageously slopes inwardly, thus forming a funnel-shaped structure which facilitates the application of suction.
The probe is connected to a light measuring rod, which may be made of light metal, and which is counterbalanced so as to apply only a light load, the pressure of the system not exceding about 1 g/cm.sup.2. Means are provided for applying weights to the measuring rod, thus providing for the possibility to increase the starting pressure to a predetermined value. The measuring rod is connected to a suitable measuring device of high sensitivity and low inertia, thus making possible measurements in the lower range of the stress-strain curve. Advantageously the measuring rod is connected to a Linear Variable Differential Transformer (LVDT), means being provided for recording the output of the LVDT with adequate sensitivity. Recording means were tested giving about half-scale deflection per 1 mm indentation for a certain range of measurements. A recorder having a moving sheet of recording medium was used. The speed of movement of the paper can be adjusted according to the accuracy of the record desired.